1. Field of the Invention
This invention relates to a graphic information retrieval system, and more particularly to a system for retrieving a part of a graphic information such as a map recorded on a recording medium in reduced scale and displaying the retrieved part thereof in a display device in enlarged scale.
2. Description of the Prior Art
Drawings or figures bearing two dimensionally extending graphic information such as maps, circuit diagrams, piping plans and other kind of plans like blueprints are usually divided into several pages to facilitate the handling thereof. One of this kind of information divided into a number of pages is an atlas. The atlas includes a map of small reduction ratio in addition to a number of detailed maps of comparatively large reduction ratio so that a desired detailed map can easily be found. In a microfilm system, a map is divided into several image frames of a microfilm. Therefore, in practical use of the atlas or the microfilm map viewing system, it is necessary to turn the pages or to feed the frames several times to find a desired spot in the map. It is possible to connect a computer to a microfilm reading system to perform a direct retrieval of a spot of the map. However, this will need a great capacity of memory, which results in a great increase in the cost. Further, it is often desired to see a map along a road extending over several pages. In such a case, it takes a long time and needs a troublesome turning of the pages or feeding of the frames to see the map as desired.
Particularly in case of emergency in a police office, for instance, finding a spot on a map upon receipt of an emergency phone or the like, it is often desired to guide a squad car to the spot by viewing a road map. In other emergency works such as fire services, gas, water and electricity services also, it is required to quickly find the spot concerned.